Anticoagulants, Their Laboratory Monitoring, and Reversal

Anticoagulant therapy has undergone substantial evolution over the past century, progressing from early parenteral agents such as heparin to vitamin K antagonists (VKAs) and, more recently, to direct oral anticoagulants (DOACs). This review provides an overview of the major classes of anticoagulants, including unfractionated heparin (UFH), low molecular weight heparin (LMWH), fondaparinux, direct thrombin inhibitors, VKAs, and DOACs, with emphasis on their mechanisms of action, clinical applications, laboratory monitoring, and reversal strategies. While UFH remains widely used in acute settings, its unpredictable pharmacokinetics and risk of heparin induced thrombocytopenia have led to increased use of LMWH and fondaparinux. VKAs, historically the cornerstone of oral anticoagulation, are limited by variable dosing requirements and the need for routine monitoring. In contrast, DOACs have transformed anticoagulation management through predictable pharmacokinetics, fixed dosing, and improved safety profiles, and are now first line therapies for several thromboembolic conditions. The development of targeted reversal agents, including protamine, vitamin K, prothrombin complex concentrates, idarucizumab, and andexanet alfa, has significantly enhanced the safety of anticoagulant therapy in the setting of major bleeding or urgent procedures. Laboratory assessment remains critical for selecting anticoagulants and evaluating clinical scenarios, with evolving roles for anti-Xa assays, thrombin-based assays, and mass spectrometry techniques. Emerging anticoagulants targeting factors XI, XII, and XIII represent a promising future direction with the potential to further reduce bleeding risk while maintaining efficacy. Overall, continued advances in anticoagulant pharmacology, monitoring, and reversal strategies are driving a shift toward safer and more individualized patient care.